1. Field of the Invention
The present invention relates to graft polymers comprising polymers, containing alkylene oxide units, and open-chain N-vinylcarboxamides, processes for their preparation and the use of the graft polymers in the production of paper, board and cardboard, as dispersants for pigments and as starch cationizing agents.
2. Description of the Background
U.S. Pat. Nos. 4,880,497 and 4,978,427 each disclose the production of paper having high dry strength and wet strength, a hydrolyzed copolymer which is obtainable by copolymerization of N-vinylformamide and ethylenically unsaturated monomers, for example vinyl acetate, vinyl propionate or an alkyl vinyl ether, and hydrolysis of from 30 to 100 mol % of the formyl groups of the copolymer with formation of amino groups being used as a strength agent either on the surface of the paper or in the paper stock prior to sheet formation. The hydrolyzed copolymers are used in amounts of from 0.1 to 5% by weight, based on dry fibers.
EP-A-0 363 319 discloses graft polymers which are obtainable by free radical polymerization of unsubstituted or N-substituted acrylamide or methacrylamide and N-vinyl-substituted amides or vinyl esters of a saturated aliphatic monocarboxylic acid in the presence of adducts of alkylene oxides with a trihydric or polyhydric aliphatic alcohol of 3 to 10 carbon atoms. The graft polymers are used as dyeing assistants for coloring cellulose fibers with substantive dyes or reactive dyes.
U.S. Pat. No. 5,334,287 discloses graft polymers which are obtainable by free radical polymerization of N-vinylcarboxamides, preferably N-vinylformamide, and, if required, other monomers in the presence of monosaccharides, oligosaccharides, polysaccharides or derivatives of each of these and, if required, hydrolysis of the polymerized N-vinylcarboxamide group with formation of vinylamine units.
The graft polymers are used as dry strength and wet strength agents in the production of paper, board and cardboard.